Materials and Methods: Forty one horse strains of Streptococcus equi zooepidemicus from the laboratory stock collection of Microbiology Department of the Veterinary Faculty, Selçuk University were evaluated by the biofilm formation using three different methods: Congo red agar, crystal violet staining method and scanning electron microscopy (SEM).

Results: Incompatibility between the results obtained from Congo red agar and crystal violet staining methods was detected. Nineteen out of 31 positive strains gave strong positive on Congo red agar while 30 of them were considered as strongly biofilm producing strains in crystal violet staining method. The biofilm production was confirmed and the biofilm layers were detected by using the SEM microscope.

Conclusion: Equine clinicians in this Country should be aware of that Streptococcus equi zooepidemicus isolates are capable of forming biofilm in vitro.